A lens of variable power comprising a chamber partially bounded by an elastic membrane and filled with a fluid is for example known from document EP 2 034 338.
It is proposed in this document to make the volume of the chamber vary (by moving mechanical elements) in order to modify the pressure of the fluid and thus deform the membrane.
This solution is thus based on an elastic deformation of the membrane via stretching, which allows a spherical shape to be given thereto, and it is therefore very suitable when it is desired to make the spherical power of the lens along a given optical axis vary.
The obtainment of an astigmatism is in contrast more complex in such a system since it for example requires the use of a membrane made of a non-uniform and/or anisotropic material.